Resuspension of radionuclides into the atmosphere due to forest fires

Two major wild fire episodes occurred in north-western Russia in April/May and August 2008. The burning biomass and heating of the surface soil released several hazardous components into the atmosphere. During the spring smoke episode the Cs-137 activity concentration in the air in southern Finland increased by a factor of 10 compared to values just before the episode. Simultaneously there was an increase of a same order of magnitude in the concentrations of PM10, trace metals (e.g. lead), polycyclic aromatic hydrocarbons (e.g. benzo[a]pyrene) and potassium. The Po-210/Pb-210 activity ratio increased from the usual 3-5% to even as high as 35% because Po is more volatile than Pb. The summer episode was less severe but still the mercury concentration in the air increased by a factor of two while Cs-137 activity concentration rose by a factor of eight. From the radiological point of view the exposure to the increased radionuclide concentration was insignificant compared to health hazards due to the increased concentration of aerosol particles and their chemical components.